The present invention concerns a dial including brilliants, appliques or other applied elements and more particularly a watch dial including such decorative elements having a flat base surface. The invention also concerns a method for securing decorative elements applied to a dial.
Watch dials having applied decorative elements, intended to form time signs, on one of their faces, are already known.
A first manufacturing technique for these dials consists in securing the decorative elements, generally cut stones, between two rings each having a seat, and driving the assembly thereby formed into a hole arranged in the dial. Such a technique is described for example in Swiss Patent No. CH 260 123. This technique has the drawback however of requiring the making and handling of numerous parts of very small dimensions, which necessitates skilled labour and leads to high cost prices.
Another conventional technique for securing decorative elements including a flat base surface consists in gluing, using a liquid or semi-liquid glue, the decorative elements via their base surface into recesses made in the thickness of the dial at predetermined locations. Although less expensive than the previous technique, this technique nonetheless has numerous drawbacks.
A first drawback is that it is difficult to glue the decorative elements in an automated manner because of the small dimensions of the decorative elements in question. By way of indication, the brilliants commonly used to form the time signs have diameters of the order of 2 mm. The operations for gluing each decorative element, between one and twelve per dial according to the particular case, must be performed manually, which significantly increases the manufacturing costs of such dials.
A second drawback lies in the fact that it is difficult to determine accurately the quantity of glue to be deposited in each recess to achieve satisfactory adhesion, i.e. adhesion during which the quantity of glue deposited is neither too great, which would be liable to cause an overflow onto the useful face of the dial when the decorative element is set in place, nor insufficient, which would be liable to lead to detachment during subsequent use.
This method is also particularly disadvantageous when such dials are mounted in monoblock watch cases made of plastic closed by an ultrasound welded crystal. Indeed the Applicant has observed that, during welding of the crystal onto the case, the ultrasound vibrations propagate into the glue securing the decorative elements onto the dial, and tend to split the layer of glue and inadvertently separate said decorative elements from their settings.
The known methods thus have general industrialisation problems which need to be overcome.
The main object of the invention is thus to provide a dial, such as a watch dial, including applied decorative elements which is simple and inexpensive to manufacture.
Another object of the invention is to provide a method for securing decorative elements to a dial, this method enabling the decorative elements to be fixed securely to the dial while being easily automated and simple to implement.
The invention thus concerns a dial, in particular for a timepiece, including a plate having at least one housing in which a decorative element or suchlike is secured, characterised in that the housing includes a bottom formed of an adhesive strip, the adhesive face of said strip being in contact with said decorative element.
As a result of these features, the ultrasound vibrations can be dampened by the intrinsic flexible properties of flexibility of the strip and can thus remove the problem of breakage of the layer of glue holding the decorative elements on the dial.
The invention also concerns a method for securing decorative elements on a dial, characterised in that it includes the steps consisting in:
providing a dial or a plate in which a plurality of dials will be cut;
making in said dial or said plate, at the locations intended to receive said decorative elements, openings passing through the thickness of the dial or said plate;
applying an adhesive strip onto the bottom face of the dial or said plate, so that the face of the adhesive strip including the adhesive material is directed towards said openings;
placing said decorative elements in the openings so that they are glued via one of their faces onto the adhesive face of the strip.
As a result of these features, all the problems of the prior art linked to machining recesses and determining the quantity of glue are eliminated, and the decorative elements can be easily secured simply by applying them to the bottom of the openings of the dial provided for this purpose which is formed by the adhesive face of the strip.